How will hurricane Milton’s track and intensity affect the extent and distribution of storm surge losses from the event?

While Hurricane Milton is currently forecast to weaken to a Category 3 hurricane before it makes landfall in Florida, its large wind field combined with the susceptibility of the west coast of the state to storm surge means that it has the potential to result in a record-breaking storm surge in the region – which could be a major driver of losses.

The consensus of the forecasts has Milton making landfall just south of Tampa Bay near Bradenton, with the National Hurricane Center (NHC) forecasting storm surge heights above ground of 10-15 feet between Anclote River and Englewood, including the high-exposure Tampa Bay region. However, there remains uncertainty in the precise landfalling location.

The location and severity of the most damaging storm surge are still very uncertain due to the range of forecast track and intensity.

With ten forecast scenarios (including storm surge hazard) Moody’s HWind enables us to explore this uncertainty, not only from a hazard perspective but also in terms of the magnitude and distribution of loss when run against industry exposure within the Risk Modeler application on the Intelligent Risk Platform.

For example, within our latest HWind forecasts including storm surge (initialized at 0000 UTC on Tuesday, October 8) there are scenarios where losses are both significantly higher and lower than those modeled from the NHC’s parameters.

While still significant, the scenarios with the least potential for storm surge loss have Milton tracking much farther south, making landfall near Cape Coral, with a lower intensity of Category 1 or 2.

This combined with the majority of the surge hazard affecting regions that are both less susceptible to surge and with lower exposure towards the Everglades results in lower losses.

The scenarios with the highest potential for storm surge losses make landfall north of the entrances to either Tampa Bay or Charlotte Harbor as a major hurricane.

This is not only due to the higher projected intensity but also the position of the wind field funneling the surge into these bays, which concentrate and amplify the incoming water leading to higher surge levels. This combined with the higher concentration of exposure in these regions results in the higher forecasted losses.

HWind customers can explore the implications of these different forecast scenarios, not only on modeled industry losses which are delivered via email as a summary PDF, but also within Risk Modeler where these scenarios can be run against individual portfolios to assess the range of potential losses from Milton for both wind and storm surge.

Additionally, if a user does not have the ability or appropriate exposure to run these scenarios with the North Atlantic Hurricane Models, they can approximate the magnitude of loss by running accumulation analyses for HWind wind and surge hazard footprints within ExposureIQ, and apply custom damage ratios by hazard band (3-second peak gust and surge elevation respectively) and risk characteristics (e.g. construction and occupancy).